docs: def getid(self, ref):
          """Obtain the reference number of the vgroup following the
          vgroup with the given reference number .
  
          Args::
  
            ref    reference number of the vgroup after which to search;
                   set to -1 to start the search at the start of
                   the HDF file
  
          Returns::
  
            reference number of the vgroup past the one identified by 'ref'
  
          An exception is raised if the end of the vgroup is reached.
  
          C library equivalent : Vgetid
                                                      """
  
          num = _C.Vgetid(self._hdf_inst._id, ref)
          _checkErr('getid', num, "bad arguments or last vgroup reached")
          return num